1. Field Of The Invention
Broadly, this invention relates to traffic monitoring and in a specific embodiment to a system for controlling traffic lights at traffic intersections by detecting and processing vibrations actuated by a vehicle passing over a vibration generator. In another specific embodiment, the invention relates to a system which utilizes a vibration receiver to detect vibrations and a processor to convert the vibrations into a control signal which triggers traffic lights.
2. Description Of Related Art
A well-known fixture at traffic intersections is the common "traffic light," which traditionally has three "light elements," red, yellow, and green. Traffic lights are typically used to prevent collisions at intersections, to determine which vehicle has the right-of-way, and to control traffic flow.
Many, if not most, traffic intersections have a predetermined timing mechanism that sets a time for the traffic light's green light element, yellow light element and red light element to be activated. The various traffic lights at the intersection are coordinated by the timing mechanism to control traffic flow. For example, when vehicles traveling in one direction through an intersection see a green light, vehicles traveling through the intersection in a way that could result in a collision are faced with a red light. With this mechanism, the time that a traffic light remains in one state, i.e., the time the green light element is activated, before switching to the other element is often preselected based on the anticipated traffic flow through the intersection. For example, if a large business street intersects with a small residential street, then the traffic timing mechanism and traffic lights may be preset to activate the green light element for the business street for longer time than for the residential street.
Other traffic light systems have a variable timing mechanism that is responsive to the actual flow of traffic. These systems are far superior in terms of controlling traffic flow since the often inaccurate estimation of anticipated traffic flow can be eliminated and the actual traffic flow can trigger the timing of the traffic lights. For example, these systems may utilize an actuating element that is disposed and embedded in a traffic-bearing surface. For example, traffic lights at intersections are often connected to inductive loops. The inductive loops provide a signal responsive to the presence of a vehicle passing over the loops. However, these and other types of embedded element systems have various shortcomings. They are costly and inconvenient since the road surface must be excavated in order to implant the sensors. For example, it is not unusual for mere sensor installation of such an embedded system to be highly expensive, which is, of course, borne by the taxpayer. Consequently, it may be cost prohibitive to install such system at an intersection. Further, since the actuating elements, e.g., the inductive loops, are physically connected to the processor and controller of the traffic light system, these systems are, for the most part, permanent, thus preventing easy removal and implementation at another location.